Beside the developments of endoscopic managements for common bile duct stones, common bile duct exploration, choledochotomy and t-tube replacement into the common bile duct continue to be frequently used treatment methods. T-tubes also provide a convenient access for monitoring postoperative biliary complications. However, common bile duct exploration and t-tube replacement itself is the cause of significant morbidity. In this report, a 45 year old female patient with choledocho-pancreatic fistula which developed after cholecystectomy due to injury of common bile duct is presented. At ERCP, the contrast medium which was introduced via the t-tube was observed passing through the fistula between the common bile duct and pancreatic duct. This fistula was also shown after selective cannulization of the common bile duct. It was thought that the fistula probably developed due to injury of the common bile duct during exploration with metallic probes and that the t-tube was misplaced through this false route. This complication was treated with endoscopic sphincterotomy and three weeks later at control ERCP, the fistula had completely closed.